Echinoidea and Crinoidea

Question 1

Echinoidea morphology

Answer 1

Ossciles fused to form test - covering in hard shell
Spines used in movement (as well as podia), can be controlled by mutable connective tissue
Gills sticking out for gaseous exchange
Have pedicellaria for keeping animal clean - like starF
Aristotles lantern - modified ossicles form chewing device - teeth-like structures

Question 2

Echinoideas different forms

Answer 2

Sea potato - burrowing sea urchins, has less harsh spines (look furry)
-known as irregular urchins = more bilateral symmetry
-mouth moved more forward and anus slightly backward
-podia used for respiration
-burrowing makes them differ in form
Extreme case in sand dollars - they burrow too

Question 3

Crinoidea features

Answer 3

Most ancient group
Sessile and collect food with arms
Only group with mouth on top
Both have a calyx - filled with ossicles (showing they are present)

Question 4

Sea lilies

Answer 4

Sea lilies have stalk - cannot move

• unfurl arms to feed
• have podia used for feeding, act as cilia to pass food to mouth
• found in deep sea (once very common)

Question 5

Feather stars

Answer 5

Feather stars have become secondarily mobile - can move to certain extent by waving their arms around
-lost their stalk
Feed same way as lilies